First, make sure you’re getting the same kind of coolant that’s already in your car. You don’t want to switch suddenly—it’s not good for your vehicle. You should also check your owner’s manual to see how much coolant your radiator holds. That way you know how much to buy.

Once you’ve bought your coolant, it’s time to flush it. When the car is completely cooled, jack the car up so that you can get underneath it. Next, find the radiator cap, and put a pan underneath it to drain the fluid into. Don’t let the fluid run onto the street! It’s not safe for the environment. Most cities have locations where you can safely dispose of hazardous waste.

Pop the hood of the car before you take the cap off, and clean off the radiator with soap and water. Get underneath the car and remove the cap, either using your hands or a special tool from the parts shop, so you can open the drain cock. Let the fluid drain out completely, and then flush it with water to get the last of the dirty coolant out, repeating a few times.

Next, recap the radiator and fill it with the new antifreeze, using 50% antifreeze and 50% water. Fill it up to the top, and you’re done.